1. Field of the Invention
This invention relates to medical instrumentation for surgically cutting body tissue, and more specifically, to novel electrosurgical cutting apparatus for excising a tissue specimen from a female uterine cervix by means of endocervical conization.
2. Technical Background
Cervical Intraepithelial Neoplasia (CIN), a virally-induced disease commonly found in sexually active women, has been shown to be a precursor to cervical cancer. CIN frequently occurs and often coexists in the cervix, vagina and vulva of the female reproductive system. Early diagnosis and management of CIN, therefore, is essential in the prevention of disease progression to invasive cancer.
Improvements in cytologic assessment and evaluation has led to the identification of early precursor lesions. Typically, the first clue to the presence of cervical neoplasia (e.g., tumor formations) is an abnormal Pap smear. In such tests, a small amount of tissue is usually scraped from the interior walls of the uterus and the uterine cervix and pathologically examined to determine if abnormal or pre-cancerous cells are present. If abnormal or pre-cancerous cells are found, the significant features for a diagnosis of CIN typically include cellular immaturity, cellular disorganization, nuclear abnormalities and increased mitotic activity. The extent of the mitotic activity, immature cellular proliferation and nuclear atypicality is generally used to identify the degree of cervical neoplasia.
It is important, however, to acknowledge that the histologic appearance of a lesion does not unequivocally predict whether it represents a simple productive viral infection or a neoplasm. Some low-grade lesions can be classified as productive viral infections, but others contain cancer-associated human papillomavirus (HPV) types and have the biologic features of a precursor lesion. In this regard, endocervical conization procedures have been developed by those skilled in the art for the management of CIN and precursor lesions that may progress to invasive carcinoma.
Traditionally, cervical conization procedures are performed by a surgeon using a conventional scalpel inserted through the vagina to the uterine cervix which may be secured in place by one or more surgical clamps. The scalpel is carefully manipulated in a circular pattern about the mouth of the cervix while attempting to maintain the blade at a constant acute angle relative to the cervical canal in order to cut and remove a symmetrical tissue sample. A serious disadvantage with free-hand surgical cutting techniques and methods of the prior art is that it is virtually impossible to excise an ideal tissue sample which is configured having a symmetrical shape sufficient for accurate and reliable analytical testing by a pathologist. In this regard, a prognosis is highly dependent upon the tissue sample having a constant angle about its circumference and that is symmetric (capable of division by a longitudinal plane into similar halves which correspond in size, shape and relative position on opposite sides of a dividing line or median plane or about a center or axis) about the central canal of the cervix from which it has been excised. Accordingly, the regularity and symmetry of the tissue samples collected by means of prior art free-hand techniques are generally conditional upon the skill and expertise of the surgeon.
Based on the foregoing disadvantages associated with free-hand techniques, those skilled in the art developed surgical instruments for performing endocervical conization comprising at least one cutting blade having a selectively fixed relationship to a handle member. For example, prior art surgical instruments for performing cold-knife conization of the cervix were developed consisting of a two part body having an elongated main portion, a separate distal end secured to the main portion and a pair of round nose, pivotal blades disposed on opposing sides of the main portion adjacent the distal end. In operation, the pivotal blades may be simultaneously rotated and progressively advanced or retracted by means of the combined rotary and linear motion of an actuator and internal cam assembly. These prior art cold-knife surgical instruments are generally manipulated by holding a grip in one hand and rotating a handle with the other hand, which action rotates the entire body and hence the pivotal blades. Upon revolution, the blades advance so as to produce a "helicoid" cutting path in contiguous cervical tissue.
In accordance with other such prior art apparatus and techniques for performing cold-knife conization, those skilled in the art developed surgical instruments having first and second elongated arms pivotally connected together intermediate their ends to provide for scissor-like relative movement. Mounted at one end of the first arm is a coextensive probe sized to be inserted into a female cervical canal. A corresponding end of the second arm secures a surgical cutting blade at an acute cutting angle relative to the probe with the apex of the angle located adjacent the distal end of the probe. The cutting blade can alternatively be moved toward and away from the probe by pivotal manipulation of the arms. In operation, the arms are mutually pivoted to cause the single cutting blade to pierce and slice through cervical tissue. In this manner, the instrument may be rotated gently about the longitudinal axis of the probe to move the cutting blade in a circular pattern about the cervical canal to excise a cone-shaped tissue sample for pathological study and diagnosis.
Despite the development and use of prior art cold-knife conization apparatus and techniques as described above, the overall effectiveness of such prior art devices has been questioned because of the excessive removal of healthy tissue, the uncertainty whether the full extent of the lesion has been removed, post-operative recovery time and the potential for severe bleeding. To overcome several deficiencies of prior art cold-knife devices, electrosurgical instruments were developed that provide a means for cutting and/or cauterizing body tissue while demonstrating fewer risks and complications than those associated with cold-knife conization. In particular, electrosurgical instruments and techniques generally reduce blood loss, operative time and post-operative patient recovery time.
One such prior art electrosurgical device comprises an instrument channel for slidably receiving a cutting surgical electrode disposed in the form of a loop or snare. The surgical snare may be extended or withdrawn from the end of an endoscope and made to surround an undesirable growth within a body organ or cavity by means of an actuator. To resect the growth, the snare is generally positioned around the base of the growth and tightened so as to gather the tissue where the growth adjoins the wall of healthy tissue. A meaningful advantage of electrosurgical procedures of the prior art is that they are relatively bloodless as a result of immediate cauterization of the tissue as the loop or snare electrode cuts through it.
Electrodes for endocervical conization have also been developed which include a thin triangular or linear wire extending in a straight line between a probe and a support member. A significant disadvantage with utilizing prior art electrosurgical devices for endocervical conization which comprise a triangular or linearly disposed cutting wire is that they tend to produce greater thermal injury to the specimen and intact cervical tissue than medically desirable, thus having the potential for leading to reproductive and/or obstetric sequelae. Excessive healthy tissue disposed near the proximal tip(s) of the cutting wire and the middle section of the excision are typically removed unnecessarily, thus leading to poor interpretation by pathologists because of excess thermal injury. Moreover, since CIN lesions generally extend no more than 8 mm into the cervical tissue, the removal of excess tissue results in needless thermal injury to the surrounding healthy tissue and will therefore typically lengthen post-operative recovery time.
While the prior art electrosurgical devices disclosed above may appear generally suitable for their intended purposes, these prior art electrosurgical devices nevertheless leave much to be desired from the standpoint of excessive tissue removal, thermal injury to surrounding healthy tissue and effectiveness of operation. In accordance therewith, it would be desirable as a diagnostic and therapeutic modality to provide an improved electrosurgical cutting apparatus for endocervical conization which realizes the advantages of the wire electrode while at the same time eliminating the disadvantages associated therewith.
Such an electrosurgical cutting device is disclosed and claimed herein.